| In China, the total area of desert and Gobi is 1.308 million square kilometer. It is distributed in Xinjiang, Qinghai, Gansu, Neimenggu, Shaanxi, Jilin and Heilongjiang province. With the development of economy, under the national long-term planning of railway network,it is an inevitable trend that high-speed railway is built in the vast Gobi area. The length of the 2nd LanXin railway designed with high-speed which is being constructed is about 1.8 thousand kilometers. The length in Gobi area is about 0.9 thousand kilometers. The total length of the subgrade is about 1.2 thousand kilometers. The circumstance is special. Circumstance event which is special is as follows: the drought, the windy, less and centralized rain. There are almost gravel, sandy gravel and sand fillings in Gobi area. Most of the fillings are gap-gradation and cohesionless. There are some questions for these fillings in compaction and water stability. The subgrade constructed with those is scoured seriously. At present the design method of slope surface protection is not created. The design and construction technology of non-performing filling subgrade in Gobi area is the critical question which should be resolved as soon as possible when the high-speed railway is being constructed in a large scale.Based on the 2nd LanXin railway, the particular character, construction technology, quality inspection technology, slope stability and slope surface protection design of the non-performing filling in Gobi area are researched for the purpose of those questions by means of laboratory test, field test, theoretical analysis and numerical calculation.The physical and mechanical character of the Gobi filling in the 2nd LanXin railway is acquired by test. It is the popular character that the Gobi soils filling are absence of a medium grain size and cohesionless due to little cohesive grains. The change in friction after compaction relates to the shape of grain. The friction of fine granular gravel filling is larger after compacted, while that of fine round gravel filling is almost equal. The construction and quality inspection technology is formed for the subgrade with the typical Gobi soil fillings. Because of lack of cohesive grains and a medium grain size, the compaction event for filling is as follows: no sufficient confined stress for forced soil, weak friction, not sufficient constraint, flowage and difficult compaction. Compaction should be carried out under the condition that apparent cohesion can effectively strength the constraint for adjacent soils by controlling water content. The results of K30 and Ev2 will be influenced because of flow of the adjacent soil. Subgrade compacted should be inspected as soon as possible.The measure of enhancing subgrade slope is put forward by stability analysis. The stability of slope is enhanced after the measure is implemented which the geotechnical grille whose distance between layers is 0.6 meters and whose length is 3 meters is embedded in subgrade slope. It is showed that the stability is significantly enhanced by means of the measure.The mechanism of slope surface protection is revealed. The effective norm stress from slope surface protection layer enhances the stability of slope surface. There are surface bulge, broken line sliding and downslope gravity sliding due to local lack of slope surface or its protection, in terms of underlying destroyed slope surface pattern. Based on the interaction between slope surface protection and slope surface and the limited equilibrium theory, The models used to analyze slope surface stability are created. The method of slope surface stability design and calculation is put forward.The safety factor and critical saturation depth of downslope gravity sliding, surface bulge and broken line sliding are computed when the slope surface is in the dry, saturated and seepage state for typical slope surface protection in 2nd LanXin railway. The basis for design of slope surface protection is provided. |
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